1. Field of the Invention
This invention relates to remote meter reading and meter encoder systems and more particularly to a dual mode meter reading apparatus having at least two meter encoders for providing separate meter readings from a common integrating meter for a meter telemetering system.
2. Description of the Prior Art
In the field of remote meter reading and telemetering systems, it is generally known to equip a meter to be monitored at a remote site with various types of encoders or encoding devices. A meter encoder is usually either directly responsive to the metering status of a measuring element included in the meter to be monitored or is responsive to a dial indication of the meter. In integrating type meters including odometers and consumption meters, a shaft in the meter movement defines a meter measuring element responsive to the measured quantity increases, use or consumption. Typically, utility meters, such as used for billing and usage monitoring of electric energy, gas and water consumption, include a rotatable shaft measuring element. The rate of rotations of the measuring element is proportional to the demand or rate of usage or rate of change in the measured quantity. A mechanical dial register assembly is included in the integrating meters to provide visual totalized or integrated measurement indications in units of a standard parameter. For example, electric energy meters include dial register assembles having plural order decade-related dial indicators, typically either four or five dials, coupled by a gear train to the measuring element. The dial assemblies accumulate or totalize the measuring element rotations to provide corresponding visual numerical dial readings in kilowatthours (KWH).
Encoders for integrating meters include two general types. A first type is a dial encoder providing electronic shaft angle or shaft position encoding of each of the indicator shafts of a dial register assembly. Typically, separate binary logic words are produced for each of the dial indicators to represent the same dial meter readings available by visual observations of the dial register assembly. The dial encoders usually require shaft code elements, associated sensors, sensor scanning arrangements and coding logic. The dial encoders are advantageously used for remotely reading the same dial reading as would be required by physically observing the dial register assembly at the meter site. The dial encoder outputs are also advantageously responsive to the non-volatile readings of a relatively simple and reliable dial register assembly and not be subject to loss of data by power outages or power failures. Some disadvantages of the dial encoders include minimum low order dial resolution so that the least significant digit position in the dial indicated parameter is limited to tens or units of a parameter such as kilowatthours. Still further errors in the dial encoders are sometimes undetectable such as when misalignment occurs between a dial indicator pointer and a code element assembled to a common dial shaft. Examples of dial encoders are disclosed in U.S. Pat. Nos. 3,310,801; 3,376,567; 3,484,780; 3,662,368; 3,750,122; 3,750,156; 3,846,788; 3,846,789; and 4,037,219, the last patent being assigned to the assignee of this invention.
The second general type of meter encoder is the pulse encoder having provision for sensing metering events and generating distinct pulses each responsive to a predetermined quantum of a quantity to be measured by the associated meter. Typically, a rotating measuring element of the meter drives a pattern of indicia or drives a contact device which activates an associated sensor or switch so that pulses are generated at a rate proportional to the metering rotations of the measuring element. The pulse encoders are also referred to as pulse initiators and are widely used for different measuring and monitoring applications in utility meter systems. For meter telemetering systems, the encoder pulses are typically applied to electronic counters or accumulators. The accumulated pulses are scaled or calibrated to the parameter, such as kilowatthours, defining the measured quantity. Quite importantly, the meter pulses can be produced to provide high resolution in the accumulated meter readings. Some of the disadvantages of pulse encoders include the accumulation of meter data readings in conventional volatile electronic data registers which are subject to data loss by power outages or power failures. External and internal circuit generated noise spikes and spurious pulses and pulse threshold variations at the input to the pulse counters can often produce pulse accumulation errors or failures to accumulate valid pulses so that the accumulated meter readings are inaccurate. The aforementioned error producing conditions provide a lack of correlation between the pulse encoder accumulated readings and the mechanical indications of an associated dial register assembly. Accordingly, the dial register assemblies of meters having pulse encoders are often required to be checked more often than those meters having the aformentioned dial encoders. Examples of pulse initiators for electric energy meters are described in the "Electrical Meterman's Handbook", Seventh Edition, published 1965 by Edison Electric Institute, New York, N.Y. Further examples of pulse initiator type encoders for electric energy meters are disclosed in U.S. Pat. Nos. 3,878,391 and 3,943,498, both assigned to the assignee of this invention.
U.S. Pat. Nos. 3,820,073 and 4,130,874, both assigned to the assignee of this invention, disclose remote meter reading system communication terminal arrangements utilizing either a meter pulse encoder or a meter dial encoder for remotely reading electric energy meters. The first noted patent discloses a non-volatile solid state encoding circuit for accumulating electric energy related pulses.